Analysis and Suppression on Three Phase Unbalanced Current in 220kV Ring Power Transmission Lines of Xinjiang Power Grid

Abstract

The 220kV ring transmission system in Xinjiang power grid often occurs three-phase current unbalance phenomenon. If it can not be effectively and promptly managed, it would be a threat to the normal operation of the power system. To explore the generation mechanism and control methods of three-phase unbalanced current in 220kV ring transmission lines, this paper takes ring transmission lines constructed with multi-circuit transmission lines on the same tower and non transposition , 220kV Fenghuang - East Shihezi/West Shihezi - Manasi power plant-third stage engineering of Manasi power plant, as an example to make related simulations with phase sequence adjustment, line looping-off, phase sequence transposition and reactor addition in the equivalent simulation models of PSASP and ATPDraw software . According to the analysis of the changes of three-phase current unbalance rate, multi-circuit transmission lines on the same tower and non transposition are the main reasons for producing unbalanced three-phase current. It can be effectively limit the three-phase unbalanced current of ring transmission lines by taking ring transmission lines into proper looping-off, phase sequence adjustment of multi-circuit transmission lines on the same tower, uniform transposition of all lines and reactor addition in the transmission lines with low impedance and other measures.